Many proteins exert an effect on cell growth, differentiation, and inflammation through signal transduction, mediated by binding to a cell surface receptor. Yet other proteins such as factors that initiate or are necessary for blood clot formation, act enzymatically in blood. While these actions are generally part of normal processes, under certain circumstances, it may be desirable to limit or inhibit the action of certain proteins and the effects of subsequent signaling. For example, tumor growth promoted by a growth factor, such as bFGF acting on melanoma cells, is deleterious and often leads to fatalities.
Approached to inhibit specific proteins have concentrated primarily on interfering with protein-substrate or protein-receptor interactions. Typically, this involves using an antibody or other molecule that competitively binds the protein, by administration of competitors for receptor binding, or by protease digestion of the protein. An alternative approach, not generally pursued, is to reduce the level of the protein by inhibiting its expression at a transcriptional or translational level. Methods of reducing protein levels by inhibiting the transcription or translation of the protein have been difficult to achieve because of inherent problems of inhibiting the specific expression of one or a few proteins.
The discovery that certain proteins, such as growth factors, mediators of inflammation, and mediators of blood clotting, are exported through a nonclassical secretory pathway allows the development of specific inhibitors for these proteins. These proteins are identified by their lack of a hydrophobic leader sequence that mediates secretion by the classical Golgi/ER pathway. These proteins are believed to be exported from a cell by exocytosis.
This invention provides inhibitors of the export of these leaderless proteins, allowing control of undesired proliferation and inflammation, as well as other related advantages.